title: Expression of human equilibrative nucleoside transporter 1 in mouse neurons regulates adenosine levels in physiological and hypoxic-ischemic conditions.
abstract: Activation of adenosine A(1) receptors inhibits excitatory synaptic transmission. Equilibrative nucleoside transporters (ENTs) regulate extracellular adenosine levels; however, the role of neuronal ENTs in adenosine influx and efflux during cerebral ischemia has not been determined. We used mice with neuronal expression of human ENT type 1 and wild type (Wt) littermates to compare responses to in vitro hypoxic or ischemic conditions. Extracellular recordings in the CA1 region of hippocampal slices from transgenic (Tg) mice revealed increased basal synaptic transmission, relative to Wt slices, and an absence of 8-cyclopentyl-1,3-dipropyl-xanthine mediated augmentation of excitatory neurotransmission. Adenosine (10-100 μM) had a reduced potency for inhibiting synaptic transmission in slices from Tg mice; inhibitory concentration 50% values were approximately 25 and 50 μM in Wt and Tg slices, respectively. Potency of the A(1) receptor agonist N(6) -cyclopentyladenosine (1 nM-1 μM) was unchanged. Transient hypoxia or oxygen-glucose deprivation produced greater inhibition of excitatory neurotransmission in slices from Wt than Tg, mice. The ENT1 inhibitor S-(4-nitrobenzyl)-6-thioinosine abolished these differences. Taken together, our data provide evidence that neuronal ENTs reduce hypoxia- and ischemia-induced increases in extracellular adenosine levels and suggest that inhibition of neuronal adenosine transporters may be a target for the treatment of cerebral ischemia.
authors.affiliation: Department of Pharmacology and Therapeutics, University of Manitoba, Winnipeg, Manitoba, Canada.
authors.forename: Dali
authors.initials: D
authors.lastname: Zhang
authors.forename: Wei
authors.initials: W
authors.lastname: Xiong
authors.forename: Benedict C
authors.initials: BC
authors.lastname: Albensi
authors.forename: Fiona E
authors.initials: FE
authors.lastname: Parkinson
mesh_terms: D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000241:Adenosine / Q000031:analogs & derivatives / Q000378:metabolism* / Q000494:pharmacology; D058916:Adenosine A1 Receptor Antagonists / Q000494:pharmacology; D000818:Animals; D004305:Dose-Response Relationship, Drug; D033721:Equilibrative Nucleoside Transporter 1 / Q000235:genetics / Q000378:metabolism*; D005260:Female; D005947:Glucose / Q000172:deficiency; D005978:Glutathione / Q000031:analogs & derivatives / Q000494:pharmacology; D006624:Hippocampus / Q000473:pathology*; D006801:Humans; D000860:Hypoxia / Q000473:pathology*; D066298:In Vitro Techniques; D051379:Mice; D008822:Mice, Transgenic; D009474:Neurons / Q000187:drug effects* / Q000502:physiology; D018408:Patch-Clamp Techniques; D011485:Protein Binding / Q000187:drug effects / Q000502:physiology; D058906:Purinergic P1 Receptor Agonists / Q000494:pharmacology; D018709:Statistics, Nonparametric; D009435:Synaptic Transmission / Q000187:drug effects / Q000235:genetics; D013868:Thioinosine / Q000031:analogs & derivatives / Q000493:pharmacokinetics; D014316:Tritium / Q000493:pharmacokinetics; D014970:Xanthines / Q000494:pharmacology
chemical_list: D058916:Adenosine A1 Receptor Antagonists; D033721:Equilibrative Nucleoside Transporter 1; D058906:Purinergic P1 Receptor Agonists; C527914:S-(4-nitrophenacyl)glutathione; D014970:Xanthines; D014316:Tritium; C048599:N(6)-cyclopentyladenosine; D013868:Thioinosine; C051360:1,3-dipropyl-8-cyclopentylxanthine; D005978:Glutathione; C001789:4-nitrobenzylthioinosine; D005947:Glucose; D000241:Adenosine